Updating a picture without page reload

How would I go about updating an image that gets updated on a server every couple of seconds with out the user having to hit the refresh button, my first guess was ajax but I haven't really worked with it before. Could someone point me in the right direction?

EDIT: Forgot to mention that the image is a .gif generated by a perl script - trying to grab it by url return a script

It seems there is something wrong with your Perl script. Trying to access the image by the URL should return an image anyway. It should return binary data and not a script. You should also set the Content-type header of the response to image/gif. Verify if it indeed returns binary data before trying to fix your JavaScript code.